downshifting problem
01-14-2004, 02:43 AM
#1
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downshifting problem
In my new car I just discovered this problem when downshifting into second. When I shift down into second the car shakes pretty violently unless I blip the gas then its a smooth downshift. Shifting up into all the gears is no problm and shifting down is all good except for second gear. I went through the records and saw the the PO had the clutch done around 15k ago. I've seen other post about problems shifting up into second but none about downshifting. I really don't want to take to the shop where the clutch was done because its nearly 200 miles away and I'm not really sure about taking it to the local shop cause I don't think they are 944 friendly.
Anyone have any ideas what the problem could be?
Anyone have any ideas what the problem could be?
01-14-2004, 03:00 AM
#2
Race Director
Um, I hope you're down downshifting to slow the car down....if that's the case, then,
DO NOT DOWNSHIFT TO SLOW THE CAR DOWN.
Do a search here on "Heel and toe" for the technique used to grab a lower gear while braking for a corner.
Really, you shouldn't be doing that: use your brakes to slow down, not your tranny!
HTH,
-Z-man.
DO NOT DOWNSHIFT TO SLOW THE CAR DOWN.
Do a search here on "Heel and toe" for the technique used to grab a lower gear while braking for a corner.
Really, you shouldn't be doing that: use your brakes to slow down, not your tranny!
HTH,
-Z-man.
01-14-2004, 03:08 AM
#3
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LOL Z-man, you're pretty adament about that aren't ya
...D, correct me if i'm wrong, but it sounds like you're not rev-matching when you downshift. That's a serious no-no on your clutch. If you do choose to downshift to slow down, I'd recommend heel-and-toe'ing it... and no matter how you decide to downshift, always match the revs!! Not doing so will only kill your clutch and create extra stress on the engine and drivetrain. As the 944's clutches are un-Godly expensive and a bitch to replace, I'd stick with Z-mans advice and use the brakes more to slow down... they're much cheaper and a helluva lot easier to replace! If you take your car to to track, heel-and-toe to slow down if that's what you prefer, but I'd keep it mostly for the track if I were you.
Just my $0.02 though!
-Kevin
...D, correct me if i'm wrong, but it sounds like you're not rev-matching when you downshift. That's a serious no-no on your clutch. If you do choose to downshift to slow down, I'd recommend heel-and-toe'ing it... and no matter how you decide to downshift, always match the revs!! Not doing so will only kill your clutch and create extra stress on the engine and drivetrain. As the 944's clutches are un-Godly expensive and a bitch to replace, I'd stick with Z-mans advice and use the brakes more to slow down... they're much cheaper and a helluva lot easier to replace! If you take your car to to track, heel-and-toe to slow down if that's what you prefer, but I'd keep it mostly for the track if I were you.Just my $0.02 though!
-Kevin
01-14-2004, 07:27 AM
#5
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While driving hot you should not go below3000 rpms. 1st and second are for launch or nearly a dead roll.. Your car likes 4-5 grand on the tack.. that is the power band.. push the pedal more and shift less.. step away from the 8 cylinder low rev thought.. These engines are made for high revs. It took me awhile to get used to the sound and speed..
Ignore the shift light.
Ignore the shift light.
01-14-2004, 07:27 AM
#6
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V944....I will teach you the method! All we need is several interstate exits. Cost of the tutorial is the 88 924S! j/k!
Picture this....In 4th want to go to 3rd...clutch in brake on downshift roll foot while still on brake (firmly) on to gas pedal and "punch" the throttle to increase the REV's to the speed the car is at then release the clutch and ease on the gas.
Some use the ball of the foot on the brake and roll the foot to the gas and some use the heal to kick down on the gas. Takes a lot of practice. Also these cars pedals are very close and depending on your foot size the pedal set up can be a bit mismatched so you see guys add a wider pedal or a wing on the pedal to help and assure that you are on the CORRECT pedal. Nothing worse than hitting the gas when you should be on the brakes! Dal
Picture this....In 4th want to go to 3rd...clutch in brake on downshift roll foot while still on brake (firmly) on to gas pedal and "punch" the throttle to increase the REV's to the speed the car is at then release the clutch and ease on the gas.
Some use the ball of the foot on the brake and roll the foot to the gas and some use the heal to kick down on the gas. Takes a lot of practice. Also these cars pedals are very close and depending on your foot size the pedal set up can be a bit mismatched so you see guys add a wider pedal or a wing on the pedal to help and assure that you are on the CORRECT pedal. Nothing worse than hitting the gas when you should be on the brakes! Dal
Last edited by dgz924s; 01-14-2004 at 08:07 AM.
01-14-2004, 08:40 AM
#7
Race Director
Originally posted by FSAEracer03
If you do choose to downshift to slow down, I'd recommend heel-and-toe'ing it... If you take your car to to track, heel-and-toe to slow down if that's what you prefer, but I'd keep it mostly for the track if I were you.
Just my $0.02 though!
-Kevin
If you do choose to downshift to slow down, I'd recommend heel-and-toe'ing it... If you take your car to to track, heel-and-toe to slow down if that's what you prefer, but I'd keep it mostly for the track if I were you.
Just my $0.02 though!
-Kevin
Hate to say this, the heel and toe technique is never used to slow the car down, even on the track! It's purpose is quite the opposite: it should not change the attitude of the car whatsoever.
A properly executed heel-and-toe downshift will have absolutely no effect on the decelleration of your car: it should be completely transparent: a blindfolded person sitting in the passenger seat shouldn't be able to tell when you've grabbed a lower gear. All braking is done with the brakes, none is done with the shifter.
V944God: sounds like you need to join PCA and start attending autocrosses and Driver's ed events!
HTH,
-Z-man.
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01-14-2004, 09:34 AM
#8
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Umm, I'm lost please explain what the heel and toe is for, I've heard of this technique many, many times, but don't know the reason for it.
I know my method of dropping it into the gear and releasing the clutch without touching the gas until the clutch is fully engaged isn't the right way, I haven't done this is my 944, but all my other beaters I have.
I know my method of dropping it into the gear and releasing the clutch without touching the gas until the clutch is fully engaged isn't the right way, I haven't done this is my 944, but all my other beaters I have.
01-14-2004, 09:41 AM
#9
Race Director
Have a look at this link, it may help a little bit (it has diagrams as well):
http://www.turnfast.com/tech_driving..._heeltoe.lasso
"Heel-toe Downshift
The heel-toe downshift is a fundamental technique to driving fast through corners. During a heel-toe downshift, you'll be steering with the left hand, shifting with the right hand, clutching with the left foot, and working both the brake and gas pedals with the right foot -- all at exactly the same time.
It takes some getting used to, and it takes repetitive practice to become smooth, and have it be second nature. At first it takes a lot of concentration. You're doing a lot of things at the same time. Besides working on all the controls, you also need to be sensitive to the tire grip during braking, you have to be watching your reference points heading into a corner, and to make matters worse, if you're racing, you might have to be looking for traffic. However, after a couple of weekends of practice, you'll get the hang of it, and in no time you'll be able forget about your hands and feet, and concentrate on the track.
On the street when you approach a corner, you were probably taught to complete your braking before the corner, coast through the turn, then as you straighten out from the turn downshift, and start accelerating again. This works on the street, but it is entirely too slow a process for the race track.
For racing, the time spent transitioning from braking to accelerating must be absolutely minimized. You're racing! You don't want to be wasting a bunch of time coasting while you're switching between pedals (even if it is only 1/2 of a second). To maximize the speed and smoothness through a corner, it becomes necessary to do some cockpit acrobatics and operate the steering wheel, shifter, clutch, brake, and accelerator all at the same time.
On the race track, as you approach a corner, your right foot comes off the gas pedal and presses the brake with the ball of the foot. Before the braking is done, you need to shift gears so when the braking is done you can immediately be back on the gas. When the braking is almost done, your left foot pushes the clutch pedal in, and your right hand downshifts. However, while you've been slowing down, the engine speed has dropped. If you let the clutch out now, the car will jerk severely as the engine works like a huge brake. If you're at the edge of traction limits (which you should be), you'll lose control of the car. To prevent this, something needs to rev the engine back up to the right speed before the clutch is released. The right foot is closest, so it is elected to tap the gas pedal. Even though the right foot is busy braking, you swing your right heel over the gas pedal and give it a short push (a "blip" as it is called) to rev the engine while the left foot also lets out the clutch (the ball of the right foot is still on the brake). The amount of blip, and the clutch release timing need to be perfected so there is a perfectly smooth transition when the clutch engages the engine. Meanwhile, the heel is rotated back off the gas, the ball of the right foot has still been braking, and has been easing off as the car approaches the turn-in point. The downshift should be completed before the braking is complete, and before the turn-in. As the engine and transmission are engaged, the braking reduced, and the turn-in begun as the foot makes a smooth transition back to the gas pedal. At first only enough gas is applied to sustain the initial corner speed, and then you gradually accelerate out of the corner.
The above description is the "what" and the "why" all mixed together, so let's look at the just the steps involved in the "what" part again:
Lift the right foot from the gas pedal and press the brake pedal
Just before the braking is done, the left foot depresses the clutch pedal
The right hand downshifts (the left is still on the steering wheel)
The right foot is still applying, but easing up on the brake pressure, then rotates so the heel is above the corner of the gas pedal
The right heel gives a quick push of the gas pedal to rev the engine quickly (the ball of the foot is still on the brake easing up even more)
The left foot releases the clutch, the right foot rotate off the gas
The right foot completes the braking
The right foot slides over to the gas pedal to assume the normal position only to maintain some pressure to sustain the vehicle speed through the first part of the corner. Then accelerating out of the turn.
The whole sequence above from the second bullet to the last takes less about half a second. This takes quite a bit of practice to get right. The whole idea is to transition between braking and accelerating with absolutely no delay, and with perfect smoothness. Done correctly, there should be no jerking of the car during the downshift and transition back to acceleration.
One other note about the above description. We have assumed the use of a street car, and a street transmission with synchros. If you're using a true race transmission without synchros, then you need to modify the above shifting with a double-clutch procedure. To do this, the clutch is pressed in, the shifter moved to neutral, and the clutch released. Then the accelerator is blipped, while the shifter is in neutral (again with the heel, while the ball of the foot continues to brake), the clutch pressed back in, the shifter placed in the lower gear, and the clutch released. This is required for maximum longevity of the transmission. If you expect to get in a race car some day that is likely to have such a transmission, it's a good idea to practice this shfting technique with your street car as well, even though it technically is not necessary."
http://www.turnfast.com/tech_driving..._heeltoe.lasso
"Heel-toe Downshift
The heel-toe downshift is a fundamental technique to driving fast through corners. During a heel-toe downshift, you'll be steering with the left hand, shifting with the right hand, clutching with the left foot, and working both the brake and gas pedals with the right foot -- all at exactly the same time.
It takes some getting used to, and it takes repetitive practice to become smooth, and have it be second nature. At first it takes a lot of concentration. You're doing a lot of things at the same time. Besides working on all the controls, you also need to be sensitive to the tire grip during braking, you have to be watching your reference points heading into a corner, and to make matters worse, if you're racing, you might have to be looking for traffic. However, after a couple of weekends of practice, you'll get the hang of it, and in no time you'll be able forget about your hands and feet, and concentrate on the track.
On the street when you approach a corner, you were probably taught to complete your braking before the corner, coast through the turn, then as you straighten out from the turn downshift, and start accelerating again. This works on the street, but it is entirely too slow a process for the race track.
For racing, the time spent transitioning from braking to accelerating must be absolutely minimized. You're racing! You don't want to be wasting a bunch of time coasting while you're switching between pedals (even if it is only 1/2 of a second). To maximize the speed and smoothness through a corner, it becomes necessary to do some cockpit acrobatics and operate the steering wheel, shifter, clutch, brake, and accelerator all at the same time.
On the race track, as you approach a corner, your right foot comes off the gas pedal and presses the brake with the ball of the foot. Before the braking is done, you need to shift gears so when the braking is done you can immediately be back on the gas. When the braking is almost done, your left foot pushes the clutch pedal in, and your right hand downshifts. However, while you've been slowing down, the engine speed has dropped. If you let the clutch out now, the car will jerk severely as the engine works like a huge brake. If you're at the edge of traction limits (which you should be), you'll lose control of the car. To prevent this, something needs to rev the engine back up to the right speed before the clutch is released. The right foot is closest, so it is elected to tap the gas pedal. Even though the right foot is busy braking, you swing your right heel over the gas pedal and give it a short push (a "blip" as it is called) to rev the engine while the left foot also lets out the clutch (the ball of the right foot is still on the brake). The amount of blip, and the clutch release timing need to be perfected so there is a perfectly smooth transition when the clutch engages the engine. Meanwhile, the heel is rotated back off the gas, the ball of the right foot has still been braking, and has been easing off as the car approaches the turn-in point. The downshift should be completed before the braking is complete, and before the turn-in. As the engine and transmission are engaged, the braking reduced, and the turn-in begun as the foot makes a smooth transition back to the gas pedal. At first only enough gas is applied to sustain the initial corner speed, and then you gradually accelerate out of the corner.
The above description is the "what" and the "why" all mixed together, so let's look at the just the steps involved in the "what" part again:
Lift the right foot from the gas pedal and press the brake pedal
Just before the braking is done, the left foot depresses the clutch pedal
The right hand downshifts (the left is still on the steering wheel)
The right foot is still applying, but easing up on the brake pressure, then rotates so the heel is above the corner of the gas pedal
The right heel gives a quick push of the gas pedal to rev the engine quickly (the ball of the foot is still on the brake easing up even more)
The left foot releases the clutch, the right foot rotate off the gas
The right foot completes the braking
The right foot slides over to the gas pedal to assume the normal position only to maintain some pressure to sustain the vehicle speed through the first part of the corner. Then accelerating out of the turn.
The whole sequence above from the second bullet to the last takes less about half a second. This takes quite a bit of practice to get right. The whole idea is to transition between braking and accelerating with absolutely no delay, and with perfect smoothness. Done correctly, there should be no jerking of the car during the downshift and transition back to acceleration.
One other note about the above description. We have assumed the use of a street car, and a street transmission with synchros. If you're using a true race transmission without synchros, then you need to modify the above shifting with a double-clutch procedure. To do this, the clutch is pressed in, the shifter moved to neutral, and the clutch released. Then the accelerator is blipped, while the shifter is in neutral (again with the heel, while the ball of the foot continues to brake), the clutch pressed back in, the shifter placed in the lower gear, and the clutch released. This is required for maximum longevity of the transmission. If you expect to get in a race car some day that is likely to have such a transmission, it's a good idea to practice this shfting technique with your street car as well, even though it technically is not necessary."
01-14-2004, 10:06 AM
#10
Three Wheelin'
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One very important thing is to keep your foot on the clutch while down shifting! Make certain you are in the correct gear! You are in 5th and wish to go to 4th so you down shift but you actually hit 3rd but your "blip" only made enough RPM's for 4th gear this called "over revving" and the motor RPM will go way too high and scream like a banshee then go BOOM!
So if you have your foot at the ready on the clutch as you let the clutch out and notice your engine screaming way too much or you see that you hit the wrong gear, your foot can depress the clutch to kill the over rev. Hopefully.....Down shifting and over revving is the number one cause of broken timing belts!
Do not confuse over rev with up shifting and hitting the limiter, not the same over rev........Dal
So if you have your foot at the ready on the clutch as you let the clutch out and notice your engine screaming way too much or you see that you hit the wrong gear, your foot can depress the clutch to kill the over rev. Hopefully.....Down shifting and over revving is the number one cause of broken timing belts!
Do not confuse over rev with up shifting and hitting the limiter, not the same over rev........Dal
Very valuable information, thanks, I'm gonna try this.
01-14-2004, 10:14 AM
#12
Race Director
Down shifting and over revving is the number one cause of broken timing belts!
Amen to that! Let me add that it is also detrimental to balance shaft belts. I had my balance shaft belt snap *coincidentally* at the same time I let a female friend of mine (who races motorcycles and you would think she would know how to drive) drive my car two years ago. She was doing about 65mph and threw it into second to slow it down right before a tight right hand corner (instead of hitting the brakes). The engine shuddered violently and suddenly was not running smooth anymore. Yep, tore it apart and the balance shaft belt was broken and wadded up in the corner of the belt cover.
Amen to that! Let me add that it is also detrimental to balance shaft belts. I had my balance shaft belt snap *coincidentally* at the same time I let a female friend of mine (who races motorcycles and you would think she would know how to drive) drive my car two years ago. She was doing about 65mph and threw it into second to slow it down right before a tight right hand corner (instead of hitting the brakes). The engine shuddered violently and suddenly was not running smooth anymore. Yep, tore it apart and the balance shaft belt was broken and wadded up in the corner of the belt cover.
01-14-2004, 10:21 AM
#13
Race Director
tifosiman:
Good resource! Nice further explanation!
A smooth transistion to a lower gear is the whole key to this, and most other track driving techniques.
Oh, and IMHO, it take more than a couple of short weekends to get the technique down: try a season or two!
-Z-man.
Good resource! Nice further explanation!
A smooth transistion to a lower gear is the whole key to this, and most other track driving techniques.
Oh, and IMHO, it take more than a couple of short weekends to get the technique down: try a season or two!
-Z-man.
01-14-2004, 10:43 AM
#14
Race Car
What about this. I was told it is called "double clutching." the technique is this: Let's say you're driving in 4th. Step on clutch, shift out of fourth to neutral, let clutch out, rev engine, step on clutch again and put car in third, then off clutch while getting on gas.
I have been doing this for years. Is the harmful to anything? definately makes for a smooth down shift.
I have been doing this for years. Is the harmful to anything? definately makes for a smooth down shift.
01-14-2004, 10:50 AM
#15
Race Car
Originally posted by tifosiman
One other note about the above description. We have assumed the use of a street car, and a street transmission with synchros. If you're using a true race transmission without synchros, then you need to modify the above shifting with a double-clutch procedure. To do this, the clutch is pressed in, the shifter moved to neutral, and the clutch released. Then the accelerator is blipped, while the shifter is in neutral (again with the heel, while the ball of the foot continues to brake), the clutch pressed back in, the shifter placed in the lower gear, and the clutch released. This is required for maximum longevity of the transmission. If you expect to get in a race car some day that is likely to have such a transmission, it's a good idea to practice this shfting technique with your street car as well, even though it technically is not necessary."
One other note about the above description. We have assumed the use of a street car, and a street transmission with synchros. If you're using a true race transmission without synchros, then you need to modify the above shifting with a double-clutch procedure. To do this, the clutch is pressed in, the shifter moved to neutral, and the clutch released. Then the accelerator is blipped, while the shifter is in neutral (again with the heel, while the ball of the foot continues to brake), the clutch pressed back in, the shifter placed in the lower gear, and the clutch released. This is required for maximum longevity of the transmission. If you expect to get in a race car some day that is likely to have such a transmission, it's a good idea to practice this shfting technique with your street car as well, even though it technically is not necessary."